Titanate luminescent material and preparation method therefor

ABSTRACT

A titanate luminescent material has a formula of A 1-x TiO 3 :Pr x @TiO 2 @M y ; wherein A is at least one selected from the group consisting of Ca, Sr, and Ba; M is at least one nanoparticles selected from the group consisting of Ag, Au, Pt, Pd, and Cu; 0&lt;x≦0.01; y is the molar ratio between M and Ti in A 1-x TiO 3 :Pr x @TiO 2 , and 0&lt;y≦1×10 −2 ; @ represents coating; M is a core, TiO 2  is an intermediate layer shell, and A 1-x TiO 3 :Pr x  is an outer layer shell. The titanate luminescent material has a high stability and a better luminescent performance. A preparation method of the titanate luminescent material is also provided.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a National Phase filing under 35 U.S.C. §371 ofPCT/CN2012/075197 filed on May 8, 2012, the entire contents of which ishereby incorporated by reference.

FIELD OF THE INVENTION

The present disclosure relates to the field of luminescent materials,and more particularly relates to a titanate luminescent material and apreparation method thereof.

BACKGROUND OF THE INVENTION

As compared with red sulfide low voltage electroluminescent phosphorZn_(1-x)Cd_(x)S (x=0˜1.0), titanate substrate has a good chemicalstability, and the phosphor obtained by doping rare earth luminescentcenter ions, such as CaTiO₃, has a better color purity. The coordinatesof red color of Pr³⁺ excited by photoluminescence and cathode ray are:x=0.680, y=0.311, which are very close to that of the ideal redaccording to NTSC color gamut. Considering the material stability andluminous colors, the titanate substrate phosphor activated by rare earthion is expected to replace red sulfide phosphor Zn_(1-x)Cd_(x)S andbecome a new generation of non-toxic, highly stable red FED phosphormaterial. Accordingly, it is the goal of researchers for furtherimproving the luminescent properties of this material.

SUMMARY OF THE INVENTION

Accordingly, it is necessary to provide a titanate luminescent materialwith high stability and excellent luminescent properties and apreparation method thereof.

A titanate luminescent material has a formula ofA_(1-x)TiO₃:Pr_(x)@TiO₂M_(y);

wherein A is at least one selected from the group consisting of Ca, Sr,and Ba;

M is at least one nanoparticles selected from the group consisting ofAg, Au, Pt, Pd, and Cu;

0<x≦0.01;

y is the molar ratio between M and Ti in TiO₂@M_(y), and 0<y≦1×10⁻²;

@ represents coating; M is a core, TiO₂ is an intermediate layer shell,and A_(1-x)TiO₃:Pr_(x) is an outer layer shell.

In one embodiment, 0.001≦x≦0.005.

In one embodiment, 1×10⁻⁵≦y≦5×10⁻³.

A method of preparing a titanate luminescent material includes thefollowing steps:

step one, mixing a metal salt solution and triethanolamine titaniumisopropoxide, adding a reducing agent, heating at a temperature of 120°C. to 160° C. with stirring, and obtaining TiO₂@M_(y) colloid, rinsingand drying the colloid to prepare TiO₂@M_(y) solid having a core-shellstructure, wherein M is at least one nanoparticles selected from thegroup consisting of Ag, Au, Pt, Pd, and Cu; y is the molar ratio betweenM and Ti, and 0<y≦1×10⁻²;

step two, mixing a source compound of A, a source compound of Pr, andthe TiO₂@M_(y) solid to form a mixture, calcining the mixture attemperature of 800° C. to 1200° C. and for 2 hours to 12 hours, and thenheating the mixture at temperature of 1000° C. to 1400° C. for 0.5 hoursto 6 hours in a reducing atmosphere, cooling and grinding the mixture toprepare A_(1-x)TiO₃:Pr_(x)@TiO₂@M_(y) powder, wherein A is at least oneselected from the group consisting of Ca, Sr, and Ba; 0<x≦0.01; @,represents coating; M is a core, TiO₂ is an intermediate layer shell,and A_(1-x)TiO₃:Pr_(x) is an outer layer shell.

In one embodiment, the source compound of A in step two is at least oneselected from the group consisting of oxide, carbonate, nitrate, andhydroxide of A.

In one embodiment, the source compound of Pr in step two is at least oneselected from the group consisting of oxide, carbonate, nitrate, andhydroxide of Pr.

In one embodiment, in step one, the reducing agent is dimethylformamide; and a volume of the reducing agent is 20% to 80% of the sumvolume of metal salt solution, triethanolamine titanium isopropoxide,and the reducing agent.

In one embodiment, the volume of the reducing agent is 25% to 50% of thesum volume of metal salt solution, triethanolamine titaniumisopropoxide, and the reducing agent.

In one embodiment, in step one, the TiO₂@M_(y) colloid is centrifugallyprecipitated and then rinsed with ethanol.

In one embodiment, the reducing atmosphere in step two comprises atleast one reducing gas selected from the group consisting of mixedatmosphere of nitrogen and hydrogen, carbon, carbon monoxide, and purehydrogen.

In the forgoing titanate luminescent materialA_(1-x)TiO₃:Pr_(x)@TiO₂@M_(y), the metal nanoparticles are coated byTiO₂, and TiO₂ is coated by A_(1-x)TiO₃:Pr_(x), in other words, metalnanoparticles as a core, TiO₂ as an intermediate layer shell, andA_(1-x)TiO₃:Pr_(x) as an outer layer shell, such that a titanateluminescent material with a core-shell structure is provided, thusincreasing an internal quantum efficiency thereof. Additionally, sincemetal nanoparticles are added into the titanate luminescent material,the luminous intensity is thus increased, so that the titanateluminescent material has a high stability and a better luminescentperformance. The described titanate luminescent materials can be widelyapplied to lighting, display and the like areas. The preparation methodhas many advantages, such as simple procedure, tow the equipmentrequirement, low cost, no pollution, and easy control of the reaction,such that it is suitable for industrial production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a flow chart of a method of preparing a titanate luminescentmaterial in accordance with one embodiment;

FIG. 2 is a graphical representation of cathodoluminescence spectrumunder a voltage of 1.kV of the luminescent material formed in accordancewith Example 2 (designated as #1), and the luminescent material ofCa_(0.998)TiO₃: Pr_(0.002) @TiO₂ without coating metal nanoparticles(designated as #2).

DETAILED DESCRIPTION OF THE EMBODIMENTS

Reference will now be made to the drawings to describe, in detail,embodiments of the present titanate luminescent material and preparationmethod thereof.

An embodiment of a titanate luminescent material has a formula ofA_(1-x)TiO₃:Pr_(x)@TiO₂@M_(y).

wherein A is at least one selected from the group consisting of Ca, Sr,and Ba.

M is at least one nanoparticles selected from the group consisting ofAg, Au, Pt, Pd, and Cu.

0<x≦0.01; preferably 0.001≦x≦0.005.

y is the molar ratio between M and Ti in TiO₂@M_(y), and 0<y≦1×10⁻²;preferably 1×10⁻⁵≦y≦5×10⁻³.

@ represents coating; M is a core, TiO₂ is an intermediate layer shell,and A_(1-x)TiO₃:Pr_(x) is an outer layer shell. In the presentembodiment, the TiO₂ has a spherical shape.

In the forgoing titanate luminescent material, the metal nanoparticlesare coated by TiO₂, and TiO₂ is coated by A_(1-x)TiO₃:Pr_(x), in otherwords, the titanate luminescent material uses M as a core, TiO₂ as anintermediate layer shell, and A_(1-x)TiO₃:Pr_(x) as an outer layershell, such that a titanate luminescent material with a core-shellstructure is provided, thus increasing an internal quantum efficiencythereof. Additionally, since metal nanoparticles are added into thetitanate luminescent material, the luminous intensity is thus increased,so that the titanate luminescent material has a high stability and abetter luminescent performance. The described titanate luminescentmaterials can be widely applied to lighting, display and the like areas.

Referring to FIG. 1, a method of preparing the titanate luminescentmaterial includes the following steps:

Step S1, a metal salt solution and triethanolamine titanium isopropoxideare mixed, a reducing agent is then added to the mixture. The mixture isheated at a temperature of 120° C. to 160° C. (preferably 140° C.) withstirring to form TiO_(z)@M_(y) colloid. The colloid is rinsed and driedto prepare TiO₂@M_(y) solid having a core-shell structure, where M is atleast one nanoparticles selected from the group consisting of Ag, Au,Pt, Pd, and Cu; y is the molar ratio between M and Ti, and 0<y≦1×10⁻².

The metal salt solution can be at least one soluble salt solution ofmetal selected from the group consisting of Ag, Au, Pt, Pd, and Cu.

In the present embodiment, the reducing agent is dimethyl formamide, anda volume of the reducing agent is 20% to 80% of the sum volume of metalsalt solution, triethanolamine titanium isopropoxide, and the reducingagent. Additionally, the volume of the reducing agent is 25% to 50% ofthe sum volume of metal salt solution, triethanolamine titaniumisopropoxide, and the reducing agent.

In the present embodiment, the TiO₂@M_(y) colloid is firstlycentrifugally precipitated and then rinsed with ethanol.

Step S2, a source compound of A, a source compound of Pr, and theTiO₂@M_(y) solid are mixed to form a mixture, the mixture is calcinatedat temperature of 800° C. to 1200° C. and for 2 hours to 12 hours, andthen the mixture is heated at temperature of 1000° C. to 1400° C. for0.5 hours to 6 hours in a reducing atmosphere, the mixture is cooled andground to prepare A_(1-x)TiO₃:Pr_(x)@TiO₂@M_(y) powder, wherein A is atleast one selected from the group consisting of Ca, Sr, and Ba;0<x≦0.01; g represents coating; M is a core, TiO₂ is an intermediatelayer shell, and A_(1-x)TiO₃:Pr_(x) is an outer layer shell.

The source compound of A is at least one selected from the groupconsisting of oxide, carbonate, nitrate, and hydroxide of A.

The source compound of Pr in step two is at least one selected from thegroup consisting of oxide, carbonate, nitrate, and hydroxide of Pr.

The reducing atmosphere includes at least one reducing gas selected fromthe group consisting of mixed atmosphere of nitrogen and hydrogen,carbon, carbon monoxide, and pure hydrogen.

In the present embodiment, the reducing atmosphere is at least onereducing gas of mixed atmosphere of nitrogen (N₂) and hydrogen (H₂),carbon (C), carbon monoxide (CO), and pure hydrogen (H₂).

The preparation method has many advantages, such as simple procedure,low the equipment requirement, low cost, no pollution, and easy controlof the reaction, such that it is suitable for industrial production.

The specific examples are described below.

Example 1

Preparation of titanate luminescent material ofSr_(0.999)TiO₃:Pr_(0.001)@TiO₂@Au_(1×10) ⁻ ₂ using a high-temperaturesolid-phase synthesis method is described below.

Preparation of TiO₂@Au_(1×10) ⁻ ₂: 10.3 mg of chloroauric acid(AuCl₃.HCl. 4H₂O) was weighed and dissolved into deionized water toprepare 20 mL of chloroauric acid solution with a concentration of5×10⁻³ mol/L. 5 mL of triethanolamine titanium isopropoxide with aconcentration of 4.3 mol/L was measured and diluted with isopropanol toa concentration of 1 mol/L. 10 mL of 5×10⁻³ mol/L chloroauric acidsolution and 5 mL of 1 mol/L isopropanol solution containingtriethanolamine titanium isopropoxide were mixed and stirred, 15 mL ofdimethyl formamide was added. After stirring for 15 min at a roomtemperature, the mixture was heated to 160° C. and stirred using areflux device, when the color of solution turned light brown throughcolorless and turned dark brown, the heating was stopped, the system wascooled to the room temperature, and TiO₂@Au_(1×10) ⁻ ₂ colloid wasobtained. The colloid was then centrifuged, rinsed with ethanol anddried, and TiO₂@Au_(1×10) ⁻ ₂ solid was prepared, where y=1×10⁻².

Preparation of titanate luminescent materialSr_(0.999)TiO₃:Pr_(0.001)@TiO₂@Au_(1×10) ⁻ ₂: 0.5175 g of SrO, 0.0009 gof Pr₆O₁₁, and 0.4195 g of TiO₂@Au_(1×10) ⁻ ₂ powder were weighed andground sufficiently in an agate mortar to mix evenly, the mixture powderwas then transferred to a corundum crucible, heated at 800° C. in amuffle furnace for 12 h, then sintered and reduced at 1300° C. for 4 hin a tube furnace under a H₂ reducing atmosphere. After cooling thepowder to the room temperature, titanate luminescent materialSr_(0.999)TiO₃:Pr_(0.001)@TiO₂@Au_(1×10) ⁻ ₂ was obtained.

Example 2

Preparation of titanate luminescent material ofCa_(0.998)TiO₃:Pr_(0.002)@TiO₂@Ag_(5×10) ⁻ ₄ using a high-temperaturesolid-phase synthesis method is described below.

Preparation of TiO₂@Ag_(5×10) ⁻ ₄: 3.4 mg of silver nitrate (AgNO₃) wasweighed and dissolved into deionized water to prepare 20 mL of silvernitrate solution with a concentration of 1×10⁻³ mol/L. 10 mL oftriethanolamine titanium isopropoxide with a concentration of 4.3 mol/Lwas measured and diluted with isopropanol to a concentration of 0.22mol/L. 2 mL of 1×10⁻³ mol/L silver nitrate solution and 18 mL of 0.22mol/L isopropanol solution containing triethanolamine titaniumisopropoxide were mixed and stirred, 10 mL of dimethyl formamide wasadded. After stirring for 15 min at a room temperature, the mixture washeated to 140° C. and stirred using a reflux device, when the color ofsolution turned light brown through colorless and turned dark brown, theheating was stopped, the system was cooled to the room temperature, andTiO₂@Ag_(5×10) ⁻ ₄ colloid was obtained. The colloid was thencentrifuged, rinsed with ethanol and dried, and TiO₂@Ag_(5×10) ⁻ ₄ solidwas prepared, where y=5×10⁻⁴.

Preparation of titanate luminescent materialCa_(0.998)TiO₃:Pr_(0.002)@TiO₂@Ag_(5×10) ⁻ ₄: 0.3996 g of CaCO₃, 0.0014g of Pr₆O₁₁, and 0.3196 g of TiO₂@Ag_(5×10) ⁻ ₄ powder were weighed andground sufficiently in an agate mortar to mix evenly, the mixture powderwas then transferred to a corundum crucible, heated at 1000° C. in amuffle furnace for 6 h, then sintered and reduced at 1200° C. for 4 h ina tube furnace under a 95% N₂+5% H₂ weak reducing atmosphere. Aftercooling the powder to the room temperature, titanate luminescentmaterial Ca_(0.998)TiO₃:Pr_(0.002)@TiO₂@Ag_(5×10) ⁻ ₄ was obtained.

FIG. 2 is a graphical representation of cathodoluminescence spectrumunder a voltage of 1.5 kV of the luminescent material formed inaccordance with Example 2, and the luminescent material ofCa_(0.998)TiO₃: Pr_(0.002)@TiO₂ without coating metal nanoparticles. Itcan be seen from FIG. 2 that, at an emission peak of 612 nm, theemission intensity of luminescent material coating metal nanoparticlesis enhanced by 30% comparing to Ca_(0.998)TiO₃: Pr_(0.002)@TiO² withoutcoating metal nanoparticles Ag. Accordingly, the luminescent materialaccording to Example 2 has a good stability, good color purity and highluminous efficiency.

Example 3

Preparation of titanate luminescent material of Ba_(0.995)TiO₃:Pr_(0.005)@TiO₂@Pt_(5×10) ⁻ ₃ using a high-temperature solid-phasesynthesis method is described below.

Preparation of TiO₂@Pt_(5×10) ⁻ ₃: 25.9 mg of chloroplatinic acid(H₂PtCl₆.6H₂O) was weighed and dissolved into deionized water to prepare10 mL of chloroplatinic acid solution with a concentration of 2.5×10⁻³mol/L. 5 mL of triethanolamine titanium isopropoxide with aconcentration of 4.3 mol/L was measured and diluted with isopropanol toa concentration of 0.5 mol/L. 8 mL of 2.5×10⁻³ mol/L chloroplatinic acidsolution and 16 mL of 0.5 mol/L isopropanol solution containingtriethanolamine titanium isopropoxide were mixed and stirred, 6 mL ofdimethyl formamide was added. After stirring for 15 min at a roomtemperature, the mixture was heated to 140° C. and stirred using areflux device, when the color of solution turned light brown throughcolorless and turned dark brown, the heating was stopped, the system wascooled to the room temperature, and TiO₂@Pt_(5×10) ⁻ ₃ colloid wasobtained. The colloid was then centrifuged, rinsed with ethanol anddried, and TiO₂@Pt_(5×10) ⁻ ₃ solid was prepared, where y=5×10⁻³.

Preparation of titanate luminescent material Ba_(0.995)TiO₃:Pr_(0.005)@TiO₂@Pt_(5×10) ⁻ ₃: 0.6819 g of Ba(OH)₂, 0.0034 g of Pr₆O₁₁,and 0.3196 g of TiO₂@Pt_(5×10) ⁻ ₃ powder were weighed and groundsufficiently in an agate mortar to mix evenly, the mixture powder wasthen transferred to a corundum crucible, heated at 1200° C. in a mufflefurnace for 2 h, then sintered and reduced at 1400° C. for 0.5 h in atube furnace under a carbon reducing atmosphere. After cooling thepowder to the room temperature, titanate luminescent materialBa_(0.995)TiO₃: Pr_(0.005)@TiO₂@Pt_(5×10) ⁻ ₃ was obtained.

Example 4

Preparation of titanate luminescent material ofCa_(0.99)TiO₃:Pr_(0.01)@TiO₂@Pd_(1×10) ⁻ ₅ using a high-temperaturesolid-phase synthesis method is described below.

Preparation of TiO₂Pd_(1×10) ⁻ ₅: 0.22 mg of palladium chloride(PdCl₂.2H₂O) was weighed and dissolved into deionized water to prepare20 mL of silver nitrate solution with a concentration of 5×10⁻⁵ mol/L.10 mL of triethanolamine titanium isopropoxide with a concentration of4.3 mol/L was measured and diluted with isopropanol to a concentrationof 2.5 mol/L. 5 mL of 5×10⁻⁵ mol/L palladium chloride solution and 10 mLof 2.5 mol/L isopropanol solution containing triethanolamine titaniumisopropoxide were mixed and stirred, 5 mL of dimethyl formamide wasadded. After stirring for 15 min at a room temperature, the mixture washeated to 130° C. and stirred using a reflux device, when the color ofsolution turned light brown through colorless and turned dark brown, theheating was stopped, the system was cooled to the room temperature, andTiO₂@Pd_(1×10) ⁻⁵ colloid was obtained. The colloid was thencentrifuged, rinsed with ethanol and dried, and TiO₂@Pd_(1×10) ⁻⁵ solidwas prepared, where y=1×10⁻⁵.

Preparation of titanate luminescent materialCa_(0.99)TiO₃:Pr_(0.01)@TiO₂@Pd_(1×10) ⁻⁵ : 0.6494 g of Ca(NO₃)₂, 0.0137g of Pr(NO₃)₃, and 0.3260 g of TiO₂@Pd_(1×10) ⁻⁵ powder were weighed andground sufficiently in an agate mortar to mix evenly, the mixture powderwas then transferred to a corundum crucible, heated at 1100° C. in amuffle furnace for 4 h, then sintered and reduced at 1200° C. for 6 h ina tube furnace under a 95% N₂+5% H₂ weak reducing atmosphere. Aftercooling the powder to the room temperature, titanate luminescentmaterial Ca_(0.99)TiO₃:Pr_(0.01)@TiO₂@Pd_(1×10) ⁻ ₅ was obtained.

Example 5

Preparation of titanate luminescent material of(Ca_(0.6)Sr_(0.4))_(0.996)TiO₃:Pr_(0.004)@TiO₂@Cu_(1×10) ⁻ ₄ using ahigh-temperature solid-phase synthesis method is described below.

Preparation of TiO₂@Cu_(1×10) ⁻ ₄: 1.6 mg of copper nitrate was weighedand dissolved into ethanol to prepare 20 mL of copper nitrate solutionwith a concentration of 4×10⁻⁴ mol/L. 5 mL of triethanolamine titaniumisopropoxide with a concentration of 4.3 mol/L was measured and dilutedwith isopropanol to a concentration of 2 mol/L. 2 mL of 4×10⁻⁴ mol/Lcopper nitrate solution and 4 mL of 2 mol/L isopropanol solutioncontaining triethanolamine titanium isopropoxide were mixed and stirred,24 mL of dimethyl formamide was added. After stirring for 15 min at aroom temperature, the mixture was heated to 120° C. and stirred using areflux device, when the color of solution turned light brown throughcolorless and turned dark brown, the heating was stopped, the system wascooled to the room temperature, and TiO₂@Cu_(1×10) ⁻⁴ colloid wasobtained. The colloid was then centrifuged, rinsed with ethanol anddried, and TiO₂@Cu_(1×10) ⁻⁴ solid was prepared, where y=1×10⁻⁴.

Preparation of titanate luminescent material(Ca_(0.6)Sr_(0.4))_(0.996)TiO₃:Pr_(0.004)@TiO₂@Cu_(1×10) ⁻⁴ : 0.1817 gof Ca(OH)₂, 0.0485 g of Sr(OH)₂, 0.0027 g of Pr₆O₁₁, and 0.196 g ofTiO₂@Cu_(1×10) ⁻⁴ powder were weighed and ground sufficiently in anagate mortar to mix evenly, the mixture powder was then transferred to acorundum crucible, heated at 900° C. in a muffle furnace for 3 h, thensintered and reduced at 1000° C. for 6 h in a tube furnace under a COreducing atmosphere. After cooling the powder to the room temperature,titanate luminescent material(Ca_(0.6)Sr_(0.4))_(0.996)TiO₃:Pr_(0.004)@TiO₂@Cu_(1×10) ⁻⁴ wasobtained.

Example 6

Preparation of titanate luminescent material of Ba_(0.994)TiO₃:Pr_(0.006)@TiO₂(Ag_(0.5)/Au_(0.5))_(1.25×10) ⁻ ₃ using ahigh-temperature solid-phase synthesis method is described below.

Preparation of TiO₂@(Ag_(0.5)/Au_(0.5))_(1.25×10) ⁻ ₃: 6.2 mg ofchloroauric acid (AuCl₃.HCl.4H₂O) and 2.5 mg AgNO₃ were dissolved in 28mL deionized water to prepare 30 mL of mixed solution of chloroauricacid and silver nitrate with a sum metal concentration of 1×10⁻³ mol/L(each of chloroauric acid and silver nitrate had a concentration of0.5×10⁻³ mol/L). 2 mL of triethanolamine titanium isopropoxide with aconcentration of 4.3 mol/L was measured and diluted with isopropanol toa concentration of 0.4 mol/L. 5 mL of 1×10⁻³ mol/L mixed solution ofchloroauric acid and silver nitrate and 10 mL of 0.4 mol/L isopropanolsolution containing triethanolamine titanium isopropoxide were mixed andstirred, 10 mL of dimethyl formamide was added. After stirring for 15min at a room temperature, the mixture was heated to 150° C. and stirredusing a reflux device, when the color of solution turned light brownthrough colorless and turned dark brown, the heating was stopped, thesystem was cooled to the room temperature, andTiO₂@(Ag_(0.5)/Au_(0.5))_(1.25×10) ⁻ ₃ colloid was obtained. The colloidwas then centrifuged, rinsed with ethanol and dried, andTiO₂@(Ag_(0.5)/Au_(0.5))_(1.25×10) ⁻³ solid was prepared, wherey=1.25×10⁻³.

Preparation of titanate luminescent material Ba_(0.994)TiO₃:Pr_(0.006)@TiO₂@(Ag_(0.5)/Au_(0.5))_(1.25×10) ⁻³ : 0.7845 of BaCO₃,0.0010 g of Pr₆O₁₁, and 0.3196 g of TiO₂@Cu_(1×10) ⁻ ₄ powder wereweighed and ground sufficiently in an agate mortar to mix evenly, themixture powder was then transferred to a corundum crucible, heated at900° C. in a muffle furnace for 5 h, then sintered and reduced at 1300°C. for 4 h in a tube furnace under a 95% N₂+5% H₂ weak reducingatmosphere. After cooling the powder to the room temperature, titanateluminescent material Ba_(0.994)TiO₃:Pr_(0.006)@TiO₂@(Ag_(0.5)/Au_(0.5))_(1.25×10) ⁻³ was obtained.

Although the present invention has been described with reference to theembodiments thereof and the best modes for carrying out the presentinvention, it is apparent to those skilled in the art that a variety ofmodifications and changes may be made without departing from the scopeof the present invention, which is intended to be defined by theappended claims.

What is claimed is:
 1. A titanate luminescent material, having a formula of A_(1-x)TiO₃:Pr_(x)@TiO₂@M_(y); wherein A is at least one selected from the group consisting of Ca, Sr, and Ba; M is at least one nanoparticles selected from the group consisting of Ag, Au, Pt, Pd, and Cu; 0<x≦0.01; y is the molar ratio between M and Ti in TiO₂@M_(y), and 0<y≦1×10⁻²; @ represents coating; M is a core, TiO₂ is an intermediate layer shell, and A_(1-x)TiO₃:Pr_(x) is an outer layer shell.
 2. The titanate luminescent material according to claim 1, wherein 0.001≦x≦0.005.
 3. The titanate luminescent material according to claim 1, wherein 1×10⁻⁵≦y≦5×10⁻³.
 4. A method of preparing a titanate luminescent material, comprising the following steps: step one, mixing a metal salt solution and triethanolamine titanium isopropoxide, adding a reducing agent, heating at a temperature of 120° C. to 160° C. with stirring, and obtaining TiO_(2@)My colloid, rinsing and drying the colloid to prepare TiO₂@M_(y) solid having a core-shell structure, wherein M is at least one nanoparticles selected from the group consisting of Ag, Au, Pt, Pd, and Cu; y is the molar ratio between M and Ti, and 0<y≦1×10⁻²; step two, mixing a source compound of A, a source compound of Pr, and the TiO₂@M_(y) solid to form a mixture, calcining the mixture at temperature of 800° C. to 1200° C. and for 2 hours to 12 hours, and then heating the mixture at temperature of 1000° C. to 1400° C. for 0.5 hours to 6 hours in a reducing atmosphere, cooling and grinding the mixture to prepare A_(1-x)TiO₃:Pr_(x)@TiO₂@M_(y) powder, wherein A is at least one selected from the group consisting of Ca, Sr, and Ba; 0<x≦0.01; @ represents coating; M is a core, TiO₂ is an intermediate layer shell, and A_(1-x)TiO₃:Pr_(x) is an outer layer shell.
 5. The method according to claim 4, wherein the source compound of A in step two is at least one selected from the group consisting of oxide, carbonate, nitrate, and hydroxide of A.
 6. The method according to claim 4, wherein the source compound of Pr in step two is at least one selected from the group consisting of oxide, carbonate, nitrate, and hydroxide of Pr.
 7. The method according to claim 4, wherein in step one, the reducing agent is dimethyl formamide; and a volume of the reducing agent is 20% to 80% of the sum volume of metal salt solution, triethanolamine titanium isopropoxide, and the reducing agent.
 8. The method according to claim 7, wherein the volume of the reducing agent is 25% to 50% of the sum volume of metal salt solution, triethanolamine titanium isopropoxide, and the reducing agent.
 9. The method according to claim 4, wherein in step one, the TiO₂@M_(y) colloid is centrifugally precipitated and then rinsed with ethanol.
 10. The method according to claim 4, wherein the reducing atmosphere in step two comprises at least one reducing gas selected from the group consisting of mixed atmosphere of nitrogen and hydrogen, carbon, carbon monoxide, and pure hydrogen. 